1. Field of the Invention
The present invention pertains to a method of creating a hydrogel covalently bound to the extracellular matrix. More specifically, this invention is directed to a polymer hydrogel covalently bound to an extracellular matrix, and to a method for creating such a hydrogel, in a tissue-initiated polymerization.
2. Background Art
Integration of biomaterials with the body is a longstanding problem in medicine. Lack of proper integration with the body sacrifices implant longevity and function. Hard tissues such as cartilage and bone present particular challenges to integration.
Cartilage lacks the ability to repair itself, and has a dense extracellular matrix that provides a smooth surface with weight bearing function, making cartilage extremely challenging to integrate with other materials. Collagen fibers present in the cartilage matrix and throughout the body have structural integrity and are therefore a target for anchoring and biomaterial integration.
Earlier work (e.g. Langer et al., U.S. Pat. No. 6,224,893; Hubbell et al., U.S. Pat. No. 6,258,870; Hubbell et al., U.S. Pat. No. 6,465,001) on biological applications for polymers relied on photoinitiators to capture light energy and form free radicals to initiate polymerization of the polymer precursors. For example, in U.S. Pat. Nos. 6,258,870 and 6,465,001, the use of ethyl eosin is recommended. An advantage of certain embodiments of the present invention, wherein appropriate free radicals are produced following localized mild oxidation of the tissue, is that no photoinitiator is required, saving complexity and expense, and alleviating any issue of toxicity of the photoinitiator.
Most notably, the polymers of the prior art (e.g. Langer et al., U.S. Pat. No. 6,224,893; Hubbell et al., U.S. Pat. No. 6,258,870; Hubbell et al., U.S. Pat. No. 6,465,001) do not bind covalently to the tissue. This profoundly limits the strength and durability of these inventions, as they do not integrate well as possible with the tissue.